Multiple Pass Ultrasound Tightening of Skin Laxity of ORIGINAL ARTICLE H

ORIGINAL ARTICLE
Multiple Pass Ultrasound Tightening of Skin Laxity of
the Lower Face and Neck
HYOUN SEUNG LEE, MD, PHD,* WOO SUN JANG, MD,† YOUNG-JOO CHA, MD, PHD,‡ YOUNG-HWAN
CHOI, BE,§ YOONSIK TAK, BE,§ EENJUN HWANG, PHD,§ BEOM JOON KIM, MD, PHD,† AND MYEUNG
NAM KIM, MD, PHD†
BACKGROUND Skin laxity is a common complaint of patients who request skin rejuvenation. Radiofrequency and infrared light are widely used for nonablative treatment of skin laxity. Intense focused ultrasound (IFUS) has been investigated as a tool for the treatment of solid benign and malignant tumors for
many decades but is only now beginning to emerge as a potential noninvasive alternative to conventional
nonablative therapy.
OBJECTIVES
To evaluate the efficacy of IFUS for the treatment of face and neck laxity.
METHODS Twelve female volunteers were enrolled in the study, and 10 were ultimately evaluated. The
device under investigation was an IFUS. Areas treated included the face and neck. For treatment, the
4-MHz, 4.5-mm probe was used first, followed by the 7-MHz, 3.0-mm probe. Two blinded, experienced clinicians evaluated paired pretreatment and post-treatment (day 90) photographs. Patient self-assessments
were also obtained.
RESULTS On the first primary outcome measure, two blinded clinicians felt that 8 of 10 subjects (80%)
showed clinical improvement 90 days after treatment. Nine of 10 subjects (90%) reported subjective
improvement.
CONCLUSIONS
IFUS has many advantages for skin tightening.
The authors have indicated no significant interest with commercial supporters.
R
edundant facial, neck, or body laxity is a
feature of aging. As such, skin laxity is a
common complaint of patients requesting skin rejuvenation. Until recently, the only treatment option
for skin laxity was surgery. As technology continues to evolve, minimally invasive techniques are
gradually replacing procedures that once required
major surgical intervention.1 Recently, nonablative
treatment of skin laxity has been made possible
using devices that create uniform heating of the
dermis and the underlying tissue;2 radiofrequency
and infrared light sources are widely used for
nonablative treatment of skin laxity.
Intense focused ultrasound (IFUS) is an energy
modality that can propagate through tissues,
resulting in selective thermal coagulative changes
within the focal region of the beam while leaving
the remaining regions unaffected.3 IFUS has been
investigated as a tool for the treatment of solid
benign and malignant tumors for many decades
but is only now beginning to emerge as a potential
noninvasive alternative to conventional therapies.4
Gliklich and colleagues3 first applied IFUS to
human facial tissue, but the treatment was performed only on periauricular skin. Alam and
colleagues5 investigated IFUS for the tightening of
*
Gowoonsesang Dermatologic Clinic, Seoul, Korea; †Department of Dermatology, Chung-Ang University College of
Medicine, Seoul, Korea; ‡Department of Laboratory Medicine, Chung-Ang University College of Medicine, Seoul,
Korea; §School of Electrical Engineering, Korea University, Seoul, Korea
© 2011 by the American Society for Dermatologic Surgery, Inc. Published by Wiley Periodicals, Inc. ISSN: 1076-0512 Dermatol Surg 2011;1–8 DOI: 10.1111/j.1524-4725.2011.02158.x
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ULTRASOUND TIGHTENING
facial skin, but they evaluated only the efficacy of
IFUS for eyebrow-lift procedures using just one
pass of IFUS treatment. The most common complaints of patients requesting skin rejuvenation
involve cheek, chin, and neck laxity; no optimized
protocols exist for the treatment of these areas.
The purpose of this prospective study was to evaluate the efficacy of IFUS treatment for face and neck
laxity using a two-pass protocol.
Materials and Methods
Patients
Twelve female volunteers who provided informed
consent were enrolled in the present study. Two
subjects dropped out, leaving 10 subjects to be
evaluated. The median age of the subjects was 59
(range 55–71), and subjects had Fitzpatrick skin
types III and IV.
Exclusion criteria were active systemic or local
infections, local skin disease that might alter
wound healing, scarring in the test areas, diagnosed psychiatric illness, history of smoking, and
insertion of soft-tissue augmentation materials or
application of ablative or nonablative laser procedures within the previous 6 months.
Equipment
The investigational device was an IFUS device
(Ulthera System; Ulthera, Inc., Mesa, AZ). With
the use of ultrasound, it is possible to visualize
the skin and subcutis. After adequate visualization, a therapeutic ultrasound device can create
small (~1 mm3) geometric zones of thermal coagulation in the tissue. The source energy (0.5–1.2 J)
of the probes can be adjusted, allowing the operator to determine the depth and volume or size of
the thermally induced lesions. There are three
types of probes, with preset focus depths and
frequencies: 4 MHz, 4.5-mm focal depth (source
energy 0.75–1.2 J); 7 MHz, 4.5-mm focal depth
(source energy 0.75–1.05 J); and 7 MHz, 3.0-mm
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focal depth (source energy 0.4–0.63 J). Higher-frequency probes have been found to have greater
effects in superficial tissue comthanto lower-frequency probes. On activation and firing, each
probe delivers a series of ultrasound pulses along
a 25-mm exposure line (Figure 1A). Each individual pulse duration in the line ranges from 25 to
40 milliseconds. The spacing between thermal
coagulation points is 1.5 mm when energy is
delivered at a depth of 4.5 mm (4-MHz, 4.5-mmfocal-depth and 7-MHz, 4.5-mm-focal-depth
transducers) and is 1.1 mm when the energy is
delivered to a depth of 3.0 mm (7-MHz, 3.0-mmfocal-depth transducers).
Experimental Procedures
Topical anesthetic ointment (9% lidocaine; M’s
Well Pharmacy, Seoul, Korea) was applied to the
face and neck areas receiving treatment 45 to
60 minutes before the procedure. The anesthetic
was washed off immediately before energy delivery. Areas treated included the temples, cheeks,
submental region, and neck. The dermis and subcutaneous tissue were targeted using the 4-MHz,
4.5-mm-focal-depth and 7 MHz, 3.0-mm-focaldepth probes. For treatment, the 4-MHz, 4.5-mm
probe was used first, followed by the 7-MHz,
3.0-mm probe (Figure 1B).
Ultrasound gel was first applied to the skin. The
probe was then placed firmly on the targeted skin
surface to achieve uniform coupling with the skin
surface. The operator moved the probe parallel to
the first exposure line, placing the second row of
ultrasound exposures 3 to 5 mm from the first
line. A treatment planning card with a grid was
used to illustrate proper placement of treatment
lines to achieve a treatment density that would
produced consistent, significant lifting of tissue.
Ultrasound imaging confirmed that the probe was
acoustically coupled to the skin tissue and that
the geometric focal depth for therapy was in the
target tissue. On average, 238 exposure lines were
placed on the treated area of each subject using
LEE ET AL
Figure 1. Schematic view of the ultrasound device being applied to the skin. (A) The probe emanates a series of wedgeshaped focused ultrasound beams along a 25-mm-long exposure line and makes thermal coagulative zones. (B) The
thermal coagulation zone of the first pass (using the 4-MHz, 4.5-mm probe) extended from the superficial adipose
layer through the SMAS to the deep adipose layer. The thermal coagulation zone of the second pass (using the 7-MHz,
3.0-mm probe) extended from the deep dermis to the superficial adipose layer.
the 4-MHz, 4.5-mm probe and the 7-MHz, 3.0mm probe of the focused ultrasound system, as
indicated by the protocol. The total number of
lines was adjusted to accommodate variations in
facial size. An interval of approximately 3 mm is
appropriate to achieve good treatment density.
The total estimated treatment density on two different treatment planes (4.5 and 3.0 mm) was
approximately 20% to 25%. Complete treatment
of the face and neck required 15 to 25 minutes
per patient.
The energy setting was 1.2 J for the 4-MHz, 4.5mm-focal-depth probe and 0.63 J for the 7-MHz,
3.0-mm-focal-depth probe.
Clinical photographs of the face and neck were
taken using a digital camera (Canon EOS 40D,
Tokyo, Japan, 6.0 megapixels) before treatment;
immediately after treatment; and at 7, 30, and
90 days after treatment. Frontal, 45°, and 90° still
digital photographs of the face and neck were
obtained. Baseline photographs were displayed in a
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computer monitor for the photographer to match
the positioning of the patient as closely as possible.
Assessment
Two blinded, experienced clinicians who were not
involved in patient treatment evaluated paired
pretreatment and post-treatment (day 90) photographs of the 10 subjects in a randomized fashion
(pretreatment and post-treatment not identified as
such) to determine whether discernible clinical
improvement was noted. Each reviewer was asked
to identify the posttreatment image. If the correct
image was identified as the post-treatment image,
the assessment from the reviewer was considered
to indicate improvement; if the reviewer identified
the wrong image as the posttreatment image, the
assessment was considered to indicate detriment. If
the reviewer reported no difference between the
two photographs, the assessment was considered
indicative of no change. As such, if two reviewers
noted improvement, the patient was said to have
improved; if two reviewers noted detriment, or one
reviewer noted detriment and one reviewer noted no
change, the patient was said to have worsened; and
if two reviewers noted no change, or one reviewer
noted improvement and one reviewer noted detriment, or one reviewer noted no change and one
reviewer noted improvement, then it was determined
that no change had occurred. After this initial
assessment of the photographs, the same clinicians
reevaluated the photographs considered to represent
improvements. The reviewers were asked to score the
degree of skin laxity according to the following categories: mild improvement (improvement of superficial
laxity), moderate improvement (focal improvement
of structural laxity with or without improvement of
superficial laxity), and significant improvement
(overall improvement of structural laxity with or
without improvement of superficial laxity).
Patient self-assessments were also obtained by comparing the subjective degree of skin tightening after
treatment with that from before treatment. Patients
reported improvement as worse, none, mild, moderate, and good.
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After treatment, patients were asked to grade intraprocedure pain on a visual analogue scale from 0
to 10, with 0 denoting no pain and 10 the most
pain possible. All subjective and objective side
effects after treatment were recorded.
Results
Ten of the 12 individuals enrolled in this study
attended all required study visits. Two individuals
were lost to follow-up.
On the first primary outcome measure for efficacy of
skin tightening, two blinded experienced clinicians
judged 8 of 10 subjects (80%) as showing clinical
improvement 90 days after treatment. Two subjects
were judged to show no change (Figure 2A). The
photographs of improved patients were reevaluated
to score the degree of improvement; 2 of 8 subjects
(25%) were assessed as significantly improved, four
(50%) as moderately improved, and two (25%) as
mildly improved (Figures 2B, 3, and 4).
Patient assessments of response 90 days after treatment were as follows: 1 of 10 (10%) reported no
improvement, two (20%) reported mild improvement, five (50%) reported moderate improvement,
and two (20%) reported significant improvement
(Figure 5).
All subjects developed slight erythema and edema
immediately after treatment. Mean pain score
immediately after treatment was 3.9 ± 1.66 (range
2–7), although no subjects reported pain at any of
the follow-up visits. No other adverse events were
observed.
Discussion
As noninvasive, nonablative rejuvenation techniques have become more popular, nonsurgical
skin tightening has opened up another frontier in
aesthetic medicine. Nonablative treatment of skin
tightening is performed by heating the dermis and
underlying tissue. Collagen is the primary protein
LEE ET AL
Figure 2. Graphs displaying the efficacy of intense focused ultrasound treatment as evaluated by two clinicians. (A) Initial
results of the clinicians attempting to identify the post-treatment image. (B) Results of reevaluating the post-treatment
photographs.
(A)
(B)
(C)
(D)
Figure 3. A 59-year-old woman shows moderate improvement. (A and C) Before treatment. (B and D) Ninety days after
treatment.
in the dermis, along with subcutaneous fat septae
and the superficial musculoaponeurotic system
(SMAS). It is a family of structural proteins and is
responsible for the strength and resilience of the
skin and other tissues.6,7 Collagen fibers are composed of triple helixes of protein chains with interchain bonds that create a crystalline structure.6 As
collagen is heated, it becomes denatured. This
process is not completely understood but is thought
to involve the breakage of hydrogen bonds and
conversion from a crystalline to an amorphous
state.8 This results in thickening and shortening of
collagen fibrils, greater tissue tension due to the
rubber-elastic properties of collagen, and ultimately
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ULTRASOUND TIGHTENING
(A)
(B)
(C)
(D)
Figure 4. A 62-year-old woman shows significant improvement (A and C) Before treatment. (B and D) Ninety days after
treatment.
Figure 5. Graph of patient
90 days after treatment.
assessment
of
response
tissue tightening.8 After the initial effects, the skin
initiates a wound healing response, resulting in
the formation of new collagen, which provides
longer-term tightening of the skin.2
The attractive features of nonablative skin tightening are limited postprocedure healing time, ability
to return to work or social engagements, and lower
risk of adverse events than with ablative or surgical
skin resurfacing. IFUS, like such modalities as
intense light, lasers, and radiofrequency energy, is
suitable technology for nonablative skin tightening
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DERMATOLOGIC SURGERY
and has its own distinctive characteristics. First, it
is widely believed that energy delivery to the deeper subcutaneous layers of the face, or even the
SMAS, is most effective in inducing skin tightening.5 Second, IFUS is able to spare the epidermis
and avoid damage to the papillary dermis without
simultaneous skin cooling while creating a zone of
thermal coagulation deep within the reticular dermis and subcutaneous layers.4 The focused field
produced by IFUS vibrates tissue and creates friction between molecules. These molecules absorb
the mechanical energy, leading to the secondary
generation of heat. Selective coagulative changes
are produced within the focal region of the beam,
but other tissue proximal and distal to the focal
region of the ultrasound field is preserved.5 Third,
absorption of IFUS energy is independent of
chromophores such as melanin and hemoglobin.4
Therefore, IFUS may be helpful in overcoming
some of the difficulties encountered with
light-based treatment of darker skin types.4
A number of studies have reported on the measurement of skin thickness at different facial locations
LEE ET AL
using different methods. Despite the specimento-specimen variability of skin thickness, in
general, the skin is thickest on the cheeks, followed
by the forehead.5 On average, the epidermal thickness of facial skin is 0.03 to 0.04 mm, and the skin
thickness (epidermis + dermis) of the face is 2 to
3 mm.9,10 Macchi and colleagues11 observed that
the subcutaneous tissue of the face consists of a
superficial adipose layer, SMAS, a deep adipose
layer, and deep fascia. They also found that total
subcutaneous tissue thickness is 3 to 7 mm,
superficial adipose thickness is 1.5 to 3.5 mm,
and SMAS thickness is 0.35 to 0.45 mm
(Figure 1B).
We created a new treatment protocol for our study.
Two treatment passes were performed using two
different probes. The first pass was performed using
a 4-MHz, 4.5-mm-focal-depth probe. White and
colleagues12 evaluated thermal coagulation zones
and observed that the depth of the thermal coagulation zone was extended from 4.5 mm to 5.5 mm
when the 4.4-MHz, 4.5-mm-focal-depth IFUS
probe was used at 2.2 J. If the aforementioned theory is correct, the thermal coagulation zone of the
first pass extended from the superficial adipose
layer through the SMAS and finally to the deep adipose layer (Figure 1B). The second pass was performed using a 7-MHz, 3.0-mm-focal-depth probe.
Data regarding the thermal coagulation zone produced by this probe could not be found, but if it
produces similar effects to the 4-MHz, 4.5-mmfocal-depth probe; the thermal coagulation zone of
the second pass extended from the deep reticular
dermis to the superficial adipose layer (Figure 1B).
The thermal coagulation zone is an inverted cone
shape, and average estimated area of thermal coagulation zone is 1 mm3.3,4 Although the location of
the thermal coagulation zone may differ slightly in
different regions of the face, this method can theoretically create a wider vertical zone of thermal
injury while still sparing the epidermis and papillary dermis. Because IFUS affect double layers of
the dermis and subcutaneous tissue, this protocol
may be more effective than one-pass protocols for
skin tightening. A previous clinical study performed
by Alam and colleagues5 used a one-pass protocol
and found that 86% of subjects showed clinical
improvement. In our study, 80% of subjects were
found to show clinical improvement, but Alam and
colleagues5 evaluated the efficacy of an eyebrow lift
procedure, whereas we evaluated the efficacy of
treatment of skin laxity of the face and neck. Therefore, the results of these two studies cannot be
directly compared. In our study, we did not lower
the fluence with multiple-pass treatment. In contrast, Bogle and colleagues13 who performed a clinical study of radiofrequency tightening, lowered the
fluence with multiple-pass treatment. IFUS creates a
focused zone of thermal coagulation while
preserving the areas proximal and distal to this
zone. As such, when IFUS skin tightening is performed, the fluence does not need to be lowered,
but in most multiple-pass skin tightening procedures using other energy sources, the fluence must
be lowered.
What remains unclear is why some treated individuals respond well to treatment, whereas others do
not. In our nonresponsive individuals, IFUS may
have contracted the lax skin, but the small amount
of excess skin relative to the underlying structure
constrained the degree of visual effect.
IFUS has many advantages for skin tightening, but
only two clinical studies (including the present
study) regarding IFUS have been performed. Future
studies should be performed to assist in the creation of new devices and protocols that maximize
the advantages of IFUS.
Acknowledgments This study was supported by
a National Research Foundation of Korea grant
funded by the Korean government (2011-0008687).
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Address correspondence and reprint requests to: Beom
Joon Kim, MD, PhD, Department of Dermatology,
Chung-Ang University Hospital, 224-1, Heukseok-Dong,
Dongjak-Gu, Seoul 156-755, Korea, or e-mail:
beomjoon@unitel.co.kr